Calling an app junk to justify is argument is unconvincing. Its still a widely used app that works as good as the competition. In the case of slack, their optimisation endeavour seems to cost them quite a lot. But sure I don't have the number. If they would have start the project in Tauri or Wails at the beginning, would that saved them the refactoring? I don't now. But we will need more team using that kind of alternative to gain the knowledge and real benefit.
At this point I rewriting a toy project from electron to wails and its great. But well, it's only a toy project.